Warren Peace
Australia missed its first
chance to wipe out the rabbit scourge. Now, 50 years on, it
has another. Can it seize the moment?
By
LISA CLAUSEN Hattah-Kulkyne
For decades
the dunes of the Hattah-Kulkyne National Park were bare of
green growth, their exposed rose-pink soils shifting and sliding
in the wind and rain. Even where eucalypts and other trees
survived, the undergrowth was reduced in patches to gnawed
stubble. Not anymore: now new life is rippling through this
eroded and depleted landscape in northern Victoria. Saplings
of rosewood, native cypress pine and acacia stand slender
in the winter sunlight. Pale green shrubs crouch next to sturdy
native grasses, yellow and brown and plump with seeds. They
form a precious mosaic, for some are species that have not
germinated here for more than a century. Chief park ranger
Phil Murdoch picks his way through the erupting groundcover
and finds plants previously unrecorded here. Last year he
saw his first bluebell. He waves an arm across the huge semi-arid
space. "This whole place is changing," he says.
This wouldn't
be happening in Hattah, or in places like it around the country,
but
for a dramatic reduction in the past six years of one animal:
the wild European
rabbit. A handful were released on a Victorian property in
1859, and by 1886 their progeny had reached Queensland. Since
then, rabbits have spread across the country in a plague that
has withstood every remedy. But in 1995 came the best chance
in half a century for a massive assault on the rabbit by the
deliberate spread of rabbit calicivirus disease (rcd), also
known as rabbit hemorrhagic disease. Swiftly lethal, it tore
through Australia's wild rabbits and has reduced the national
population, experts say, by at least half. Where it's worked
best, the virus is allowing the landscape to slowly recover
from years of degradation. But some experts fear government
inaction may prevent the disease's potential from being fully
realized.
Australia's
battle against Oryctolagus cuniculus has been long and costly.
Farmers, park rangers and land managers have ripped (destroyed)
warrens and shot, trapped, poisoned, fumigated and cursed
the rabbit, but it has continued to flourish-feasting on seedlings,
crops, saplings, bark and grasses; competing with stock and
native animals for food and habitat. "You're forever chasing
your tail when you're dealing with such large areas," says
Peter Sandell, a Parks Victoria ecological management officer
in Mildura, who oversees a million hectares of national park.
"It was difficult to see how we would ever get on top of the
problem." Despite the 1950s release of the viral disease myxomatosis,
by the mid-1990s rabbits infested most of Australia south
of the Tropic of Capricorn. Along the way, they had contributed
to environmental disasters like soil erosion and the local
extinction of native fauna in places like Hattah-Kulkyne:
10 of the 22 local mammal species found there in the 19th
century have vanished. At the same time, they had plagued
farmers-it's estimated that nine rabbits eat as much as one
sheep -causing about $600 million worth of agricultural damage
each year. Trevor Ablett, a ranger with Wentworth's Rural
Lands Protection Board, grew up in western New South Wales
and remembers the hopelessness many felt about tackling the
rabbit nightmare: "It was such a big job-where would you start?"
first recorded
in china in 1984, the lethal virus later spread to Europe.
Brian Cooke, now a principal research scientist at the csiro
and a leading expert on rcd, saw it at work there and argued
for its introduction into Australia. It had an embarrassing
start, escaping in October 1995 from quarantined trials on
South Australia's Wardang Island. From there it spread at
a phenomenal rate-up to 90 km a week-and within eight months
had reached every mainland state and territory. Rabbit numbers
plummeted by up to 95%, and in many areas have remained extremely
low. "It's been a big transition," says Peter Kelly, who manages
350,000 hectares of state forest in northern Victoria, "going
from seeing rabbits all the time to getting a shock when you
see one."
While some
people were happily shocked, others were asking when they
would have that pleasure. That's because the impact of the
virus, which is spread mainly by insects and by contact between
rabbits, has varied widely. The highest mortality rates, of
90-95%, have been in drier areas where annual rainfall averages
less than 300 mm. In cooler, more humid areas the effect has
been, for reasons not fully understood, patchy or negligible.
But across large tracts of northern Victoria, western New
South Wales, inland Western Australia, central Australia and
most of South Australia, rcd is widely praised. Arriving in
central Australia in 1996, it spread "like a wildfire," says
Will Dobbie, project officer at the Centralian Land Management
Association, which covers about 300,000 sq. km of central
Australia. "It's done a magnificent job." Rabbit numbers at
eight monitoring sites in the region fell by 90%, and despite
some high-rainfall years-which normally spark breeding -have
changed little. "They've had every opportunity to come back
and they haven't," says Dobbie. That's meant the regrowth
of natives like umbrella and Queensland blue grass, and the
first regeneration of mulga trees in 50 years.
Judith Murphy
arrived on Idracowra station, a cattle property south-east
of Alice Springs, in 1954 and with husband Leo watched rabbits
become a plague. Nothing was spared-from bush and feed to
backyard daisies and citrus trees-and nothing the Murphys
did, from trapping to releasing myxomatosis, broke the rabbits'
stranglehold for long. Now they're astounded by what they
see. "Every time I go out there I see something new flowering,"
says Judith. "I've seen nothing like it in all these years.
I'm glad I've lived to see it." At Rex Fuller's De Rose Hill
cattle station, across the border in S.A., rabbits used to
drop from the branches of old mulga trees. Warrens scarred
three-quarters of his 1,800-sq.-km property and dust storms
caused by erosion were common, but "there was nothing we could
do about the rabbits," says Fuller. "They ate more than the
cattle did." After rcd killed 90% of the rabbits, "the only
bit of dust we get now is when someone drives along the road."
Signs of
recovery are everywhere in western N.S.W., too, says Ron Rees.
His family have had properties near Ivanhoe since 1878, and
Rees watched his father fighting rabbit plagues in the 1930s.
His three sons run the family properties now, but Rees travels
widely in the region and "I see only improvement in the landscape
-box trees, apple bush, belah and a lot of young trees I've
never seen before." Though some of the new vegetation is weed,
"we get feed now where there was never feed before." Rees
says most landholders won't increase stocking rates: "Getting
rid of rabbits means you can run what you already have with
better lambing percentages, better wool and you won't be so
badly affected by droughts."
There's
evidence from around the country of the change underway: from
orchids reappearing in the Coorong National Park in South
Australia's south-east to mulga on the remote Nullarbor Plain.
Phil Murdoch used to call acacias "lollipops" because rabbits
at Hattah couldn't resist them; now they're appearing unscathed
across the landscape. The park's annual budget for rabbit
control was $A250,000 before rcd arrived; now it's $A45,000.
"Plants that were once considered rare are now relatively
common," says Sandell, who has measured rcd's impact in his
region since 1996. "Our hope is that vegetation will recover
under its own steam without our intervention. But we'll probably
never see it recover completely."
The damage
done to fragile semi-arid and arid zones has been severe.
At places like Hattah, several generations are simply missing
from the tree line-there are old and dying trees and the saplings
which have shot up in the past few years, but not many in
between. The damage has been compounded by stock, goats and
kangaroos, but the rabbit has been the chief culprit. Some
species, like the mulga, which can reach 200 years of age,
will need more than a decade of respite for seedlings to grow
tall enough to survive gnawing. But it's hoped that, if rabbits
can be held in check long enough, the plants will regain a
foothold.
The same
is true of native animals pushed out by rabbits. There are
already hopeful signs: in the Coorong National Park, where
rcd is endemic, common wombats are thriving now that they
don't have to vie with so many rabbits for native grasses.
At Roxby Downs in central S.A., more grass seeds and fewer
of the rabbit's predators-not a single fox was found at Roxby
for two years after rcd arrived-has seen native hopping mice
reappear and become the area's most common small mammal, says
John Read, land manager for Western Mining Corp., which operates
the 100-sq.-km mining lease at Roxby. Elsewhere, there's less
use of poison baits, which often inadvertently killed native
fauna, and fox and feral cat numbers are expected to fall
away. In S.A.'s Flinders Ranges National Park, intensive pest
control and six outbreaks of rcd have cleared rabbits from
an area of 150 sq. km-and, it's thought, helped increase numbers
of the dasyurid, a mouse-sized marsupial, and yellow-footed
rock wallabies.
The strength
of the ecological recovery clearly depends on the continued
strength of the virus. "It's a matter of how long it's going
to last," says the csiro's Brian Cooke. He says there is no
sign
rabbits are developing inherited resistance, but there's no
guarantee that rcd's effectiveness won't eventually wane-as
did that of myxomatosis, which, though still a useful weapon,
now has a mortality rate as low as 50%. Some land managers
are already worried by community complaints that rabbits are
slowly reappearing. Ranger Peter Kelly has heard those stories
and, though the reported numbers aren't anything like those
seen before rcd, "you start to get nervous," he says.
Phil Murdoch at Hattah, John Read at Roxby, and Rex Fuller
at De Rose Hill station all say rabbit numbers on their land
are creeping up. Murdoch is pessimistic: "We might get a couple
more good years out of the virus and then be back to spending
[$A250,000] a year again." He's infuriated by local landholders
who, he says, haven't got rid of the stragglers the virus
missed. Peter Kelly also worries that "people tend to think
it's all over, that the war is finished. We have to keep reminding
people that they have the potential to make a comeback." The
rabbit is both fecund (a doe can produce on average six kittens
a month) and insatiable: in S.A.'s Gammon Ranges in 1997,
rabbits at a density of just one per square kilometer ate
half of all mulga seedlings that regenerated, says Robert
Henzell, of the state's Animal & Plant Control Commission.
That indicates how risky complacency would be. As Nicki de
Preu, National Parks & Wildlife Service ecologist for the
Flinders Ranges, says: "It doesn't take many rabbits for them
to be a problem."
The best success has come where the virus has been backed
up with conventional controls like the practice of ripping
warrens, which destroys breeding sites but can be costly when
rabbit numbers are high. The need for follow-up work is a
lesson from Australia's experience with myxomatosis-its initial
mortality rate was even higher than that of rabbit calicivirus,
but little ripping was done in its wake and when rabbits began
developing immunity, they had plenty of warrens in which to
resume breeding. People saw myxomatosis as the final solution,
says Parks Victoria's Sandell, "and obviously it wasn't. We
have to look at biological control agents as one control among
several-we can't afford not to continue with conventional
controls as well."
That message has been heard by many, including N.S.W. farmer
Ron Rees. After the failure to build on myxomatosis' success,
he sees rcd as a priceless second chance. He remembers the
days when rabbits were "packed in like sardines" on his father's
farm-and he doesn't want to return to them. He helped set
up the South West Rabbit Control Group in 1996, which, with
government and landholder funds, has since ripped 230,500
warrens on 154 properties. "We don't know how long it will
be effective for," he says, "and we can't miss the opportunity
we've got." At a cost of $A7 a warren, the project has tackled
heavy infestations-such as one 100-hectare patch containing
800 warrens, each housing about 10 rabbits. The problem is,
some areas of outback Australia are too vast or inaccessible
to rip, says ranger Will Dobbie. He says local landholders
are "all very appreciative of what the calicivirus has done,
but it's the expense [of follow-up ripping] that puts them
off."
In those areas, as Western Mining's John Read says, "we're
really in the hands of rcd." The csiro's Cooke is trying to
pinpoint how to prolong the virus' potency and boost its effect
in wetter areas. But he has spent much of the past few months
struggling to secure research funding, on top of the csiro's
contribution, for another two years' work.
That's another lesson from Australia's experience with myxomatosis:
the importance of ongoing research. The long-term effects
of "myxo" were poorly monitored-and some say the same is happening
with rcd. Since 1999, when the national surveillance program
published its final reports on rcd's impact, no national survey
has been done. Instead, what is known about the disease's
effects comes from local research projects, run on a patchwork
of government and industry funding and providing fragmentary
data. "We have not done anywhere near as well as we could
have done," Cooke says. "Any of these introductions of biological
controls are a giant experiment-and unless we assess what
happens, we're missing out on an opportunity."
In the arid and semi-arid zones where rcd has been most effective,
rainfall is highly variable and much of the flora is slow-growing,
meaning the full impact of fewer rabbits will take years to
become clear. "In effect, two years' study in that area gives
you two data points-and you can't say anything about long-term
effects on the basis of two data points," says Greg Mutze,
senior research officer at S.A.'s Animal & Plant Control Commission.
Many monitoring projects, such as one looking at the return
of small native vertebrates to the Coorong, which was refused
$A13,000 in funding last year, have had to fold.
But it's not only the benefits of rcd that experts want to
document-there are also unknown long-term effects on predators
which relied heavily on rabbits for food, and on vulnerable
native species like mallee fowl, to which foxes seem to be
turning their attention as rabbit numbers decline. Cooke believes
it would take just one person working in each state and territory-at
a total cost of perhaps $A500,000 a year-to complete a national
analysis. But, he says, national monitoring is "that area
that really people were not willing to invest in. The argument
is that it's out there now and it will do what it will do."
Where rcd has relieved the land of its burden of ever-hungry
pests, a new ecological balance is still settling into place.
What role rabbits play in it is yet to be seen. But rcd has
given Australia a tantalizing glimpse of what could be achieved
if rabbits were finally beaten. At Roxby Downs, Western Mining,
National Parks and Adelaide University are finishing off the
fencing around a 60-sq.-km area free of rabbits and predators.
Without rabbit control, says John Read, that would not have
been possible: "We couldn't have got rid of rabbits from a
couple of square kilometers before." Now, almost a century
after they were driven out, bilbies, stick-nest rats and burrowing
bettongs have been reintroduced-and they're thriving. "We
want them to reclaim their place," Read says. The great hope
is that one day, they may be able to do so without the need
of a fence.
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